Digital radio terminals have become particularly advantageous in a number of key types of communication. High frequency point to point communications are used by, among others, cellular operators, telecommunications operators, private network operators, governments, and large telecommunications operations.
Typical of conventional microwave digital radios is the use of a cable connection between an exterior antenna/transmitter portion, sometimes referred to as the Antenna Resident Unit (ARU), and an interior portion sometimes referred to as the System Interface Unit (SIU.) In conventional radios, the modulated IF signal is fed down the cable to the Indoor Unit, subjecting the signal to degradation due to varying signal-to-noise ratios, varying cable length, deterioration of the cable, environmental factors, and so on. Such degradation can result in unacceptable signal quality. In addition, conventional radios may require that the cable connecting the SIU to the ARU be equalized, especially as cable lengths increase. Such equalization can represent significant effort and, if not done properly, can also lead to unacceptable signal quality.
As a result, there has been a longfelt need for a microwave radio system which includes a cabling architecture that avoids the signal degradation long associated with conventional systems.
An additional limitation of existing radios has been the difficulty in performing loop back diagnostics on the indoor and outdoor units. This has resulted in significant maintenance costs and time for diagnosis in the event an equipment failure occurs. In typical prior art systems, some loop back testing may be performed on the indoor unit by a processor resident in the indoor unit. However, it has historically not been possible to perform significant loop back testing of the outdoor unit remotely from the indoor unit. Given that the outdoor unit is frequently mounted at some distance from the indoor unit, and frequently at or near the top of a tower, the inability to perform remote loop back testing of the outdoor unit, including testing of the RF subsystem, has raised maintenance costs significantly. In addition, prior art systems have generally not been able to handle gracefully the acknowledgment of an alarm situation. There has therefore been a need for a microwave digital radio which can perform loop back testing of both the indoor and outdoor unit under the control of a technician operating at the indoor unit, and which can communicate specific alarm conditions only where needed and where appropriate without causing redundant alarms.